Modeling calculation and test research of switching impulse voltage discharge strength

Characteristic of switching impulse discharge plays an important role during the external insulation design of transmission and transformation project. For the determination of calculation method of switching impulse discharge strength, this paper introduces a new elasticity coefficient mathematical model based on the test research of rod-plane air gaps under 50% standard switching impulse voltage. The model is proved to be effective by t verification method. By using the concept of the gap factor, the switching impulse voltages of phase to earth and phase to phase air gaps for typical electrode were calculated, such as two bundle conductor and grading ring. It provides that, in the research distance range 2.5 m to 4.0 m, the deviations between the calculated and test results are small and the average absolute value are not higher than 4%. Calculation model given in this paper can be regarded as theoretical basis for switching impulse voltage discharge strength research, particularly helpful for design and optimization in transmission and transformation projects.